Optical splitter

ABSTRACT

A fiber optic tap system includes a first receiver module having an input port configured to receive an optical fiber. The first receiver module is operable to convert a received optical signal to an electrical signal. A first transmitter module is coupled to receive the electrical signal from the first receiver module and convert the received electrical signal to an optical signal. The first transmitter module has an output port for outputting the optical signal. A first tap module is coupled to receive the electrical signal from the first receiver module.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 14/676,212,filed Apr. 1, 2015, which application claims the benefit of provisionalapplication Serial No. 61/975,414, filed Apr. 4, 2014, which isincorporated herein by reference in its entirety.

BACKGROUND

The present disclosure relates generally to fiber optic systems.

Fiber optic communication systems are becoming prevalent in part becauseservice providers want to deliver high bandwidth communicationcapabilities (e.g., data and voice) to customers. Fiber opticcommunication systems employ a network of fiber optic cables to transmitlarge volumes of data and voice signals over relatively long distances.Fiber cables are connected between switching devices so that data can betransported between the switches. In some fiber optic systems it isnecessary or desirable to “copy” or “tap” the data being transported inthe optical channel. This copied data is then used for traffic analysisand other maintenance purposes.

SUMMARY

In accordance with aspects of the present disclosure a fiber optic tapsystem includes a first receiver module having an input port configuredto receive an optical fiber. The first receiver module is operable toconvert a received optical signal to an electrical signal. A firsttransmitter module is coupled to receive the electrical signal from thefirst receiver module and convert the received electrical signal to anoptical signal. The first transmitter module has an output port foroutputting the optical signal. A first tap module is coupled to receivethe electrical signal from the first receiver module.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating aspects of an example fiber optictap system in accordance with the present disclosure.

FIG. 2 is a block diagram illustrating further aspects of an examplefiber optic tap system in accordance with the present disclosure.

FIG. 3 is a block diagram illustrating an example of fiber optic tapsystem mounted on a printed circuit board.

FIG. 4 is a perspective view illustrating aspects of an example of amodular fiber optic tap system.

FIG. 5 is an exploded view of portions of the modular fiber optic tapsystem shown in FIG. 4.

FIG. 6 is a cross section view of portions of the modular fiber optictap system shown in FIGS. 4 and 5.

FIG. 7 is a top view of portions of the modular fiber optic tap systemshown in FIGS. 4-6.

FIG. 8 is a block diagram illustrating an example of a modular fiberoptic tap system employing SFP/SFP+ ports.

FIG. 9 is a block diagram illustrating another example of a modularfiber optic tap system employing SFP/SFP+ ports.

FIG. 10 is a block diagram illustrating an example of a fiber opticsystem having bi-directional data flow.

FIG. 11 is a block diagram illustrating an example of a fiber optic tapsystem for a fiber optic system having bi-directional data flow.

FIG. 12 is a block diagram illustrating aspects of an example tap moduleused in the system shown in FIG. 11.

FIG. 13 is a block diagram illustrating an example of a modular fiberoptic tap system employing QSFP/QSFP+ ports.

FIG. 14 is a block diagram illustrating another example of a modularfiber optic tap system employing QSFP/QSFP+ ports.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as top,bottom, front, back, etc., is used with reference to the orientation ofthe Figure(s) being described. Because components of embodiments can bepositioned in a number of different orientations, the directionalterminology is used for purposes of illustration and is in no waylimiting. It is to be understood that other embodiments may be utilizedand structural or logical changes may be made without departing from thescope of the present invention. The following detailed description,therefore, is not to be taken in a limiting sense.

Typically, passive optical splitters and couplers are used to insert a“tap” into an optical link. Passive splitters, however, can contributeconsiderable insertion loss into an optical link. This reduces theoverall length that can be supported, which can handicap multi-modeapplications. Since the operational range of optical devices used inhigh speed optical links (in terms of transmit power and receiversensitivity as defined by standard specifications) is very wide,additional insertion loss may cause the overall system to operate on amarginal basis, or even not at all. Also, since the same types ofoptical transceivers are often used to monitor the tapped opticalsignals, the tapped optical signal must have a power level that iswithin range of the receiver sensitivity range of the optical signal.The result is that a user must define performance criteria and pickdevices that will work in the application.

FIG. 1 is a block diagram conceptually illustrating an example of afiber optic tap system 100 in accordance with aspects of the presentdisclosure. The illustrated fiber optic tap 100 includes a firstreceiver module 110 having an input port 112 configured to receive anoptical fiber. The first receiver module 110 is operable to convert areceived optical signal to an electrical signal. A first transmittermodule 120 is coupled to receive an electrical signal from the firstreceiver module 110, and is operable to convert the received electricalsignal to an optical signal. The first transmitter module has an outputport 122 for receiving an optical fiber and outputting the opticalsignal thereto. A tap module 130 is also coupled to receive anelectrical signal from the first receiver module 122.

In the illustrated example, the primary optical data channel isindicated by an arrow 102, showing the primary flow of data from thefirst receiver module 110 to the first transmitter module 120. It issometimes desired to “copy” or “tap” the data being transported in theoptical channel 102. This copied data is then used for traffic analysisand other maintenance purposes. The tap module 130 provides thisfunction, receiving the converted electrical signal from the firstreceiver module 110 so that the signal flowing through the primarychannel 102 can be provided via an output port 132 of the tap module 130for traffic analysis, for example.

Rather than passively split a portion of the optical signal from theprimary optical channel 102, the first receiver module 110 converts thereceived optical signal to an electrical signal. The signal for theprimary path 102 is converted from an electrical signal back to anoptical signal by the first transmitter module 120, allowing the signalto continue in the primary optical path 102. In some examples, the tapmodule 130 also converts the received electrical signal to an opticalsignal, which can be transmitted to a switch device for analysis of thesignal, for example. In other embodiments, the electrical signal fromthe first receiver module 110 is transmitted from the tap module via anelectrical conductor for analysis. The logic used to accomplish thesplitting or “copying” of data is accomplished using atransceiver/driver arrangement with and without programmable logic insome examples.

FIG. 2 illustrates further aspects of an example optical system 200employing the fiber optic tap system 100. In FIG. 2, the primary opticalpath is indicated by an arrow 202. The primary optical path 202 isprovides a two-way data path between first and second switching devices210, 220, for example. In other implementations, the primary fiber opticpath 202 could be between different types of network devices.

Since the fiber optic path 202 provides two-way data flow, two of thefiber optic tap systems 100 (labeled as 100 a, 100 b in FIG. 2) shown inFIG. 1 are employed to tap or copy data flowing in both directionsindicated by the arrow 202. Thus, optical signals flowing out of thefirst switch 210 (left to right as depicted in FIG. 1) via opticalfibers are received at an input of the first receiver module 110 a ofthe first optical tap system 100 a. The first receiver module 110 aconverts the received optical signal to an electrical signal, which isthen split into two output signals. One output signal is sent to a firsttransmitter module 120 a, which converts the electrical signal output bythe first receiver module 110 a to an optical signal. The optical signalis then output from the first transmitter module 120 a to the secondswitch 220. The second electrical signal output by the first receivermodule 110 a, which is the tapped signal, is provided to a third switch230.

Optical signals flowing from the second switch 220 to the first switch210 (right to left as depicted in FIG. 2) are received by the secondreceiver module 110 b. The second receiver module 110 b converts thereceived optical signal to an electrical signal, which is split into twooutput signals. One output signal is sent to the second transmittermodule 120 b, which converts the electrical signal output by the secondreceiver module 110 b to an optical signal. The optical signal is thenoutput from the second transmitter module 120 b to the first switch 210.The second electrical signal output by the second receiver module 110 b,which is the tapped signal, is provided to the third switch 230. In someembodiments, first and second tap modules 130 a, 130 b receive theelectrical signals output by the first and second receiver modules 110a, 110 b, respectively, and convert the electrical signals to opticalsignals that are output to the third switch 230.

In one example, the receiver and transmitter modules 110, 120, as wellas the tap modules 130 are mounted on a printed circuit board (PCB).FIG. 3 illustrates such a PCB mounted tap system 300, in which thetransmit, receive and tap modules 310,320,330 include PCB mountableadapters (LC adapters, for example) that are equipped with a TransmitOptical Sub-Assembly (TOSA) or Receiver Optical Sub-Assembly (ROSA) anda transceiver chip (XRC). Thus, the first and second receiver modules310 a, 310 b each include a ROSA that converts the received opticalsignal to an electrical signal. The electrical signal is routed to thetransmitter modules 320 a, 320 b and the tap modules 330 a, 330 b, whicheach include a TOSA that converts the received electrical signals tooptical signals using a Vertical-Cavity Surface-Emitting laser (VCSEL),Fabry-Perot (FP), Distributed Feedback Laser (DFB), or Multiple QuantumWell Laser arrangement. The modules are all mounted to a PCB 302, andthe signals are routed between the various modules using conductivetraces disposed in or on the PCB 302.

In FIG. 3, the optical signal is received by the ROSA which consists ofa positive-intrinisic-negative diode (PIN) and a transimpedanceamplifier (TIA). The PIN detects the optical signal and the changes inmodulation (usually ON-OFF KEYING or “OOK”) that cause the impedance ofthe PIN to change. These impedance changes cause a change in the currentflow through the PIN. These changes in current are measured by the TIAand converted into a usable output voltage signal. The output of theROSA is analog so the XRC is required to convert the analog signals intodigital signals and into current-mode logic (CML) signaling. In thisformat, the signal can be directed and otherwise manipulated withminimal concern over noise, latency, and signal degradation.

CML signaling is a logic level signaling format that can be fanned out(e.g., copied) to two parallel devices such as the XCR used to drive aVCSEL or FP laser diode in a TOSA assembly. A Line Driver/Receiver or1:2 CML Fanout buffer may be required to serve as a buffer interfacebetween the output of the ROSA XCR and the TOSA XCR input. The TOSA andROSA assemblies also incorporate the XCR and are interchangeable toaccommodate multi-mode to single mode media conversion.

The PCB mounted system 300 is generally low cost and compact. In someimplementations, a connection point identification (CPID) device isintegrated into the LC adapters of the ROSA and TOSA modules 310, 320,330 to provide network management and monitoring capabilities, amongother things. In such embodiments, a processor 304 monitors the CPIDlines that are on each optical port for managed connectivity support. Italso utilizes an I2C buss which is interconnected to all of the XCRdevices so the processor 304 can access real time operationalinformation about each ROSA and TOSA. The processor 304 can be a slaveto a master processor in a multi-splitter chassis configuration in whichthe master provides a web server or REST interface to enable remote datacollection. In single splitter applications the processor provides a webserver interface for remote access. The web server enables a user toaccess operational data about the splitter using any HTML web browser ona workstation or mobile device. No special application is required.

Other embodiments employ small form-factor pluggable (SFP) and/orenhanced small form-factor pluggable (SFP+) transceivers. SFP and SFP+are compact, hot-pluggable transceivers used for both telecommunicationand data communications applications. These devices interface a networkdevice (switch, router, media converter, etc.) to a fiber optic orcopper networking cable. FIG. 4 illustrates an example of a modular tapsystem 400 in accordance with disclosed embodiments. An SFP/SFP+ module410 is configured to receive an optical plug 402 such as an LC duplexoptical plug, which is connected to an optical cable 404. The module 410is received by an SFP/SFP+ connector 408 of a host device such as aswitch or router.

FIGS. 5-7 illustrate further aspects of the example module 410. Themodule 410 includes a lower shell 412 and an upper shell 414 thattogether form an enclosure 420. The enclosure 420 is fabricated usingdie cast or aluminum in some embodiments. ROSA and TOSA devices 430, 432provide the optical interface. The ROSA 430 and TOSA 432 are received inthe enclosure 420 and are mounted on a main PCB 422, which hasconductive traces configured to connect the ROSA 430 and TOSA 432 tocontacts 424, which electrically connect the module 410 to the hostdevice connector 408. In the illustrated embodiment, a CPID device 440is also situated in the enclosure 420. The CPID device 440 includes aCPID PCB 442 on which CPID components are mounted, such as a retainer444, an LED 446 and contacts 448 that engage a CPID chip 450 on thefiber optic connector 402. An EMI skirt 452 is positioned around theenclosure 420.

FIG. 8 illustrates an example data flow in a system using embodiments ofthe modular tap system 400. A primary data through path 460 is shown inthe upper portion of the diagram, where data would flow between twoswitching devices, for example. LC duplex optical plugs 402 connectoptical cables 404 to the modules 410, which are labeled 410 a, 410 b,410 c and 410 d in FIG. 8. Typical implementations could include manysuch modules. Data flows from the module 410 a to module 410 b at afirst wavelength λ₁ and from the module 410 b to the module 410 a at asecond wavelength λ₂. As noted above, the modules 410 includetransceivers that convert received optical signals to electricalsignals. A logic matrix 462 provides an electrical interface between themodules 410, routing the electrical signals output by the modules 410 asdesired. In the example shown in FIG. 8, the electrical signals from themodule 410 a are also routed to the module 410 c by the logic matrix462, where the electrical signals are converted to optical signals. Themodule 410 c thus provides tapped signals from the module 410 a of theleft to right through path 460 to tap ports for data monitoring andanalysis, for example. Copied or tapped signals from the right to leftflow path are routed from the module 410 b to the module 410 d via thelogic matrix 462, which converts the electrical signals to opticsignals.

In some examples, SFP twin axial cables (e.g., copper cables) are usedfor short tap links. FIG. 9 illustrates such an embodiment, where twinaxial cables 474 are connected to SFP/SFP+ ports 470 via twin axialcable interfaces 472 Thus, tapped signals are routed from the modules410 a and 410 b to the SFP/SFP+ ports 470.

Examples of the modular system 400 support media conversion, allowingmulti-node to multi-mode, multi-node to single-mode, multi-mode to SFPtwin axial (copper), single-mode to SFP twin axial (copper), etc. Asnoted above, some disclosed embodiments include CPID devices includingmicrocontrollers, allowing the system to be queried for real timeinformation such as launch power and received power, and accessing thesystem to enable or disable a main or tap link, for example.

FIG. 10 illustrates an example where bi-directional (BiDi)communications using 40 Gb/s aggregate bandwidth between two networkelements using multi-mode optical fiber is provided. This accomplishedby using two bi-directional 20 Gb/s channels 510,512. Each opticalchannel operates over a single multi-mode optical fiber 514 usingrespective wavelengths λ₁ and λ₂. Some typical BiDi devices use atransceiver in a quad (4-channel) small form-factor pluggable(QSFP/QSFP+) footprint, but the optical interface is a standard opticalconnector such as a duplex LC connector. Each LC port operates at 10Gb/s bi-directional for a total of 20 Gb/s per fiber (or LC port). Thisprovides an aggregate of 40 Gb/s for the entire transceiver.

FIG. 11 illustrates a system 520 using QSFP modules. The primary datapath is between a first switch 610 and a second switch 620. A thirdswitch 630 receives tapped signals via QSFP ports 632. The QSFP ports632 of the third switch 630 are used only to receive the tapped signals.As described above, the system 600 provides BiDi communications using 40Gb/s aggregate bandwidth between network devices such as the firstswitch 610 and the second switch 620 using multi-mode optical fiber overtwo bi-directional 20 Gb/s channels 510,512. The optical channels510,512 each operate over a single multi-mode optical fibers 514 usingrespective wavelengths λ₁ and λ₂. A tap coupler 640 receives opticalsignals from the optical channels 510,512 and couples a portion of theenergy from the optical channels to tap ports 642, which are connectedto the QSFP ports 632 of the third switch 630. FIG. 12 conceptuallyillustrates the tap coupler 640, wherein the bi-directional signals fromeach of the optical channels 510, 512 are routed to respective outputtap ports 642 for the first and second wavelengths λ₁ and λ₂.

FIG. 13 illustrates another example system 700 in which the modularactive tap modules 410 include QSFP ports to provide BiDi communicationsusing 40 Gb/s aggregate bandwidth. The primary data through path 760 isshown in the upper portion of the diagram, where data would flow betweentwo switching devices, for example. LC duplex optical plugs 402 connectoptical cables 404 to a plurality of active modules 710. The modules 710a, 710 b, 710 c and 710 d are similar to the modules 410 shown in FIGS.4-7, though the modules 710 include QSFP/QSFP+transceivers rather thanSFP/SFP+ transceivers. Bi-directional data flows through each opticalcable 404 in the primary through path 760 at a first wavelength λ₁ forleft to right data flow and at a second wavelength λ₂ for right to leftdata flow. The modules 710 include transceivers that convert receivedoptical signals to electrical signals, and the logic matrix 462 providesthe electrical interface between the modules 710 so that the digitaldata signals between the modules 710 a, 710 b can be coupled and copiedto other transceivers such as those used for tap modules 710 c, 710 d.The modules 710 c, 710 d convert the electrical signals to opticalsignals which are then routed to a monitor system, for example.

FIG. 14 illustrates an example in which an electrical interface (copper)is provided for the TAP ports using a data grade twin-axial cable 774 toconnect the tapped signals to the monitor system. This reduces thenumber of modules 710 required in implementations where the distancebetween the monitor system and the modules 710 is relatively short (7meters or less, for example). The twin axial cables 774 are connected toQSFP/QSFP+ ports 770 via twin axial cable interfaces 772 Thus, tappedsignals are routed from the modules 710 a and 710 b to the QFP/QSFP+ports 770 via the logic matrix 462.

As with the embodiment shown in FIG. 9, the modular system 700 supportsmedia conversion, allowing multi-node to multi-mode, multi-node tosingle-mode, multi-mode to QSFP twin axial (copper), single-mode to QSFPtwin axial (copper), etc. Embodiments of the system 700 also may includeCPID devices including microcontrollers, allowing the system to bequeried for real time information such as launch power and receivedpower, and accessing the system to enable or disable a main or tap link,for example.

The examples shown in FIGS. 8, 9, 13 and 14 include an active splitterarrangement in which multi-source agreement (MSA) standard devices suchas an SFP, SFP+, QSFP, and QSFP40G are used as the optical interface.The output or host side of the MSA devices are already in a CMLsignaling format. In some implementations, the illustrated logic matrix462 is equipped with high speed CML transceivers, a programmable logicmatrix, and a MIPS or ARM9 processor core (CPU). The programmable logicis used to route and copy the data to and from the MSA devices. The CPUinitially sets up the programmable logic which can be changed at anytime to accommodate network requirements. An example is the ability toswitch traffic from one link to another in the event there is a linkfailure. The host side of the QSFP or QSFP40G is essentially four lanesof 10 Gb/s SFP traffic, therefore the logic matrix 462 supports androutes four lanes per device. Thus, the splitter can also support a quadSFP to single QSFP aggregation by using the logic matrix to route thefour inputs to a single device.

The CPU utilizes an I2C buss interconnected to all of the MSA devices sothe CPU can access the MSA tables in each MSA device, real timeoperational information, and CPID information that can be equipped oneach MSA optical device for managed connectivity support. The CPUprovides a web server interface for remote access. The web serverenables a user to access operational data about the splitter using anyHTML web browser on a workstation or mobile device. No specialapplication is required.

As noted above, the embodiments shown in FIGS. 8 and 9 support the useof copper twin axial cable for short link SFP interconnection, and theembodiments shown in FIGS. 13 and 14 support the use of copper twinaxial cable for short link QSFP interconnection. This, in conjunctionwith the flexibility of the logic matrix, allows the SFP or QSFP activesplitter to be used as a top of rack switch.

Various modifications and alterations of this disclosure may becomeapparent to those skilled in the art without departing from the scopeand spirit of this disclosure, and it should be understood that thescope of this disclosure is not to be unduly limited to the illustrativeexamples set forth herein.

1. A fiber optic tap system, comprising: a first receiver module havingan input port configured to receive an optical fiber, the first receivermodule being operable to convert a received optical signal to anelectrical signal; a first transmitter module coupled to receive theelectrical signal from the first receiver module, the first transmittermodule being operable to convert the received electrical signal to anoptical signal, the first transmitter module having an output port forreceiving an optical fiber and outputting the optical signal thereto;and a first tap module coupled to receive the electrical signal from thefirst receiver module. 2-20. (canceled)